die

Outside an eval(), prints the value of
LIST to STDERR and exits with the current value of $! (errno). If $! is 0, exits with the value of
($? >> 8) (backtick `command` status). If ($? >> 8)
is 0, exits with 255. Inside an eval(), the error message is stuffed into
$@ and the eval() is terminated with the undefined value. This makes
die() the way to raise an exception.

If the value of
EXPR does not end in a newline, the current script
line number and input line number (if any) are also printed, and a newline
is supplied. Hint: sometimes appending ", stopped" to your message will cause it to make better sense when the string "at foo line 123" is appended. Suppose you are running script ``canasta''.

die "/etc/games is no good";
die "/etc/games is no good, stopped";

produce, respectively

/etc/games is no good at canasta line 123.
/etc/games is no good, stopped at canasta line 123.

If
LIST is empty and $@ already contains a value (typically from a previous eval) that value is
reused after appending "\t...propagated". This is useful for propagating exceptions:

eval { ... };
die unless $@ =~ /Expected exception/;

If $@ is empty then the string "Died" is used.

You can arrange for a callback to be run just before the die() does its deed, by setting the $SIG{__DIE__} hook. The associated handler will be called with the error text and can
change the error message, if it sees fit, by calling die() again. See perlman:perlvar for details on setting %SIG entries, and eval BLOCK for some examples.

Note that the $SIG{__DIE__} hook is called even inside
eval()ed blocks/strings. If
one wants the hook to do nothing in such situations, put